This invention relates to motor control devices for controlling the speed and operation of motors and, more particularly, to a control system for controlling the speed and operation of the motor of a windshield cleaning system of a vehicle.
The overall object of the system of the invention is to improve the safety of vehicle transportation. This object is accomplished with a modest cost of materials, labor and energy. The windshield wipers of the average automotive vehicle in operation today are old, worn and noisy. At the time when the driver is subjected to wet roads and surfaces, he turns on these wipers, which distract, or even mesmerize, the driver, increasing his stress and only partially establishing visability through the windshield.
It is an object of the invention to provide a control device which can be manufactured with solid state integrated circuit technology which is implemented by only a single capacitor. Since the cost of the labor to insert a capacitor in the system exceeds the cost of the capacitor itself, this object achieves a worthwhile design objective.
It is another object of the invention to provide a control device which starts immediately, when turned to on, without an inadvertent delay in wiper operation occurring.
It is a further object of the invention to provide an improved version of a prior development of the applicant. In accordance with the applicant's prior development, a dwell period is provided between the wipe cycles and, as the number of raindrops increase, while remaining insufficient to obscure visability such that intermittent operation is still a reasonable mode of wiper operation, the dwell or pause time will automatically shorten in duration. This achieves less wiper wear and less driver distraction and noise while retaining the capability of continuous wiper operation without input from the driver. This object is enhanced by changing the wiping rate in conjunction with adjusting the dwell time by a single instrument panel knob so the driver can more easily adjust the system to the operating point which meets his need while compensating for variations in vehicle manufacturing, the wearstate of the wiper rubber and contaminants on the windshield surface.
It is a further object of the invention to provide a control device which, by means of the above stated single instrument panel knob, continuously adjusts the dwell time from a maximum to zero while continuously increasing the wiping rate and then to continue to increase the wiping rate without dwell periods to the highspeed low torque capability of today's three brush DC motors, yet improving the speed torque characteristics of the motor performance by obtaining a feedback signal from the motor itself and utilizing this signal in a feedback loop to enhance the motor performance.
It is a further object of the invention to provide a control device which minimizes variation in the position of the wiper during successive pauses by utilizing a solid state switch as a controlled brake and to use this same solid state switch to conduct reverse current through the motor when the wiper motor is turned off.
It is an object of the invention to provide a control device which features depressed and/or off the glass park location of the wiper blades so as not to obstruct the vision of the driver or to interfere with the stream lines of the vehicle when the wiper operation is not required and, further, to drive the wipers to this location at low speed with the full torque capability of the motor while driving the motor in the reverse direction to utilize the mechanical mechanisms developed for this purpose.
It is an object of the invention to provide a control device which achieves this park feature without instantaneously reversing the motor rotation when the instrument panel control is placed in the off position leaving a wet streak on the glass which obscures visability. In accordance with the invention, after the control is placed in the off position, the wipers continue forward wiping the glass clean in the wipe cycle then in progress and upon reaching the on the glass pause position, the motor is reversed and the wipers move to the depressed or off the glass location by means of a single motor driven switch. The achievement of this objective further increases safety and reduces cost which is highly important in high volume products.
It is an object of the invention to solve the problems with a minimum of compatible components to incorporate the above features with the wipe after wash prior development of the applicant.
It is a further object of the invention to provide a control device to regulate the speed of a three brush electric motor under varying load conditions by utilizing two feedback loops from each of two brushes of the motor.
It is a further object of the invention to provide a control device for intermittent operation of a motor wherein the motor is deenergized abruptly at the start of a dwell period and is energized gradually to provide a "soft" start at the end of the dwell period.
It is a further object of the invention to provide a control device which conditions itself automatically during exiting of an acceptable dwell location region to vary the dwell time between wiping cycles in response to the degree of dryness of the windshield.
It is a further object of the invention to provide a control device for intermittent operation of a motor which features an "instant start" upon being energized regardless of the condition of the capacitive component of an RC timing circuit, which object is achieved by open circuiting the capacitor until the intermittent dwell position is traversed during the initial cycle of operation.
It is a further object of the invention to provide a control device for speed regulation of a three brush DC motor wherein a coarse operating motor current is established through the use of one gate of a field effect transistor (FET) and fine variations in that coarse current are established automatically through the use of a second gate on the FET.